tbuckley/cabot-search huggingface dataset:
CSIG-32. MYC DRIVEN CANCERS ARE DEPENDENT ON CONVERGENT ONCOGENIC PATHWAYS INDUCED BY GENOMIC REARRANGEMENTS AT PVT1
Authors: Anindya Bagchi
Journal: Neuro-Oncology (2023)

Abstract Plasmocytoma Variant Translocation 1 (PVT1) encodes a lncRNA that is co-amplified with MYC in multiple cancers. PVT1 is also a rearrangement hotspot in diverse human cancers with poor prognoses. However, the functional consequences of PVT1 rearrangement have remained obscure. Here we report that these genomic rearrangements often result in asymmetric enrichment of the proximal half of PVT1 (5’-PVT1) and loss of its distal half (3’-PVT1). Contrary to the general assumption of PVT1 being a non-coding RNA, we identified two distinct transcripts from the 5’-PVT1 and 3’-PVT1 that are capable of coding for functional peptides. A transcript from the retained 5’-PVT1 generates a circular RNA (CircPVT1) which codes for a previously unknown peptide, Firefox (FFX) with oncogenic properties. FFX can synergistically sensitize MYC and augment mTOR signaling in cancer cells. On the other hand, the 3’-PVT1 that is lost during the rearrangement, codes for a micropeptide, Honeybadger (HNB), with tumor-suppressive properties. Inhibition of HNB activates the RAS/MAPK signaling and enhances MYC stability by promoting phosphorylation of MYC Ser62. Molecular docking and biochemical analysis suggest that HNB can interfere with KRAS dimerization, implying its role as an allosteric modulator of RAS/MAPK signaling in cancer. We have previously revealed a strong selection and crucial cooperation between MYC and PVT1 in 8q24+ tumors. Moreover, breakpoints in PVT1 have led to PVT1 promoter-MYC fusions, found on ecDNA, resulting in promiscuous enhancer input to drive MYC transcription. Here we provide evidence that translocation events at the PVT1 locus can result into convergence of MYC, mTOR, and MAPK signaling. Taken together, our study nominates MYC/PVT1 amplification + PVT1 rearrangement as a major driver of cancer pathogenesis, and PVT1 as a critical node that coordinates MYC, mTOR, and MAPK activity in cancer, revealing new regulatory mechanisms that reshape the oncogenic landscape in tumors with genomic rearrangements at PVT1.
MODL-13. DEVELOPMENT OF TUMOR TREATING FIELDS (TTFIELDS) ARRAYS FOR TREATMENT OF HEAD TUMORS IN MICE MODELS
Authors: Sewar Zbidat, Roni Blat, Mariell Sellevoll, Martin Gabay, Inbar Schlachet, Shay Cahal, Shiri Davidi, Itai Tzchori, Adi Haber, Moshe Giladi, Yoram Palti
Journal: Neuro-Oncology (2023)

Abstract INTRODUCTION Glioblastoma (GBM) is the most common malignant brain tumor. Tumor Treating Fields (TTFields) therapy is an approved treatment for GBM, delivered continuously by two array pairs placed on the skin surrounding the tumor region. Currently, most GBM animal models are based on mice. Since arrays for TTFields application to the mouse head are lacking, GBM-TTFields in vivo studies are limited. The small dimensions and specific geometries of the mouse head make the development of such arrays challenging. METHODS We tested different array layouts to identify one that will optimally accommodate the geometries of the mouse head while minimally restricting head movement. Additionally, we investigated adhesive tapes for array attachment to the skin, to allow good adherence and hence provide efficient treatment delivery. To validate that the selected array layout delivers therapeutic field intensity to the desired region, we performed simulations and fields measurements. RESULTS To overcome the issue of small head size we developed a layout in which the arrays on the head were divided into two smaller disks, with the opposing arrays situated on the mouse torso. We also identified a thin and transparent adhesive tape that facilitated the correct positioning of the arrays on the mouse head, offered good tackiness, and allowed for easy removal without leaving residual adhesive on the skin. The arrays met the minimum treatment requirements: field intensity ≥ 1 V/cm RMS, current ≥ 50 mA, usage ≥ 75%. CONCLUSIONS Our newly developed mouse head arrays are a flexible construct, that adheres strongly to the skin to enable efficient electric field delivery. By facilitating TTFields delivery to the heads of mice, we will expand the scope of GBM treatment research and will contribute to further advance this field.
IMMU-51. THE LANDSCAPE OF TUMOR INFILTRATING T CELLS (TILS) OF CHILDHOOD BRAIN TUMORS
Authors: Itay Raphael, Michal Nisnboym, Chaim Sneiderman, Zujian Xiong, Ian Pollack, Maria Chikina, Dhivyaa Rajasundaram, Gary Kohanbash
Journal: Neuro-Oncology (2023)

Abstract T lymphocytes have a unique ability to recognize a vast array of antigens prompt by an enormous T cell receptor (TCR) repertoire. Characterization of tumor-infiltrating T cells (TILs) and their TCRs is key to understand MHC-restricted anti-tumor immunity and for developing T cell centered immunotherapies such as adoptive cell therapy and tumor vaccines. In the current work, we investigated RNAseq data from nearly 1,000 pediatric brain tumor patients and performed the first large-scale comprehensive examination of the immunogenomic and TCR landscape of TILs across the spectrum of pediatric brain tumors. We show that the relative ratio between T cell diversity (clonality) and T cell abundance within each sample, represented by the clonal expansion index (CEI), is a strong predictor of prognosis across tumor types and molecular subtypes. Interestingly, we found that CEI was strongly associated with molecular subgroups of medulloblastoma but not with known genomic features of these subgroups. Analysis of single-cell (sc)RNAseq and scTCRseq data of TILs across several tumor types, validated clonal expansion of TILs which were frequently associated with effector-cytotoxic T cell phenotypes, whereas non-expanded TILs were associated mostly with CD4 T cell phenotypes. Investigation of T cell clones recognizing a common recurrent tumor-antigen across patients based on CDR3 homology and characteristics, reveals several T cell specificity groups which are tumor type restricted with defined HLA dominance. Using machine learning investigations of genomic profiles of the patients which contain these T cell specificity groups identified novel putative HLA-restricted tumor antigens shared across patients. Importantly, our framework grounded the foundations for developing a precision medicine approach of T cell centered immunotherapies. In all, our findings have major implications for understanding the interplay between T cell and tumor genomic, and for improving immunotherapy strategies for childhood brain tumors.
CTIM-25. EO2401 PEPTIDE IMMUNOTHERAPY + NIVOLUMAB +/- BEVACIZUMAB IN FIRST RECURRENT GLIOBLASTOMA: THE PHASE 1/2 EOGBM1-18/ROSALIE STUDY (NCT04116658)
Authors: David Reardon, Ahmed Idbaih, Maria Vieito, François Ghiringhelli, Agostina Stradella, Ghazaleh Tabatabai, Michael C Burger, Iris Mildenberger, Ulrich Herrlinger, Patrick Wen, Mehdi Touat, Antje Wick, Macarena González, Alice Hervieu, Marta GilMartin, Mirjam Renovanz, Cécile Gouttefangeas, Ana Maia, Christophe Bonny, Jean-Michel Paillarse, Laurent Chêne, Jan Fagerberg, Wolfgang Wick
Journal: Neuro-Oncology (2023)

Abstract EO2401 expands existing memory T cells recognizing protein sequences from gut bacteria, which cross-react with tumor associated antigens (TAAs). EO2401 contains three CD8 HLA-A2 epitopes with mimicry to glioblastoma-TAAs (IL13Rα2, BIRC5, and FOXM1) and the CD4 epitope UCP2. Patients received EO2401 (300μg/peptide, q2weeks x4, then every 4weeks) with nivolumab (3mg/kg, q2weeks) in cohorts: C1a (n = 21, Ex2→EN; option for symptom directed low-dose bevacizumab [sLDB; 5mg/kg, q2weeks] as anti-edema treatment); C2a/1 (n = 23, EN); C2a/2 (n = 15, EN+sLDB); C2b (n = 6, adjuvant EN+sLDB); C2c (n = 9, neoadjuvant ENx2→surgery→adjuvant EN+sLDB); C3 (n = 26, EN+bevacizumab, q2weeks, 10mg/kg). EO2401/nivolumab+/-bevacizumab safety profile consistent with profile of nivolumab, and when applicable bevacizumab, except the addition of local administration site reactions which occurred in 39% of patients; 96% of events Grade 1/2 and 4% Grade 3. Immune monitoring (peripheral blood, ELISPOT, tetramer assessments) demonstrated expanded mimic specific CD8 T cells with cross-reactivity against the targeted human TAAs. In C2a/1 (83% tested) and in C3 (81% tested), 89% and 95% of tested patients showed expansion. Expansions were early (week 2 after starting EO2401), durable (up to 23 months), and robust (approximately 30% of all peripheral CD8 T cells were mimic specific in 3 clinical responders). In C2c, surgery specimens after two EO2401/nivolumab doses showed increased tumor T cell infiltration versus pre-treatment tumor in 5 of 6 patients. Addition of sLDB to EO2401/nivolumab prolonged treatment duration vs EO2401/nivolumab alone by reducing edema likely worsened by study therapy induced immune cell infiltration. Integration of bevacizumab with EO2401/nivolumab in C3 further increased efficacy in C3. C2a/1vsC2a/2vsC3: median treatment duration 1.4vs3.2vs4.8 months, disease control rate 22%vs40%vs88%, median PFS 1.6vs3.6vs5.5 months; median survival 9.0vs12.6vstoo early (C3 median FU 8.3 mo, survival ongoing up to 2 years). Further follow-up will be presented.
CSIG-06. CROSSTALK BETWEEN ONCOGENIC SIGNALING PATHWAYS AS DRIVERS OF THERAPY RESISTANCE AGAINST SMALL MOLECULE INHIBITORS IN GLIOBLASTOMA
Authors: Linde Hoosemans, Mike van Heumen, Maikel Verduin, Ann Hoeben, Marc Vooijs
Journal: Neuro-Oncology (2023)

Abstract Patients with glioblastoma multiforme (GBM) have a median survival of 15 months. Despite an intensive treatment schedule with resection, radio- and chemotherapy, recurrence is inevitable. An important challenge to overcome GBM treatment resistance involves intratumoral heterogeneity, characterized by molecularly, phenotypically, and clinically distinctive GBM subtypes. Different small molecule inhibitors have been designed to inhibit signaling proteins in oncogenic driver pathways, including the EGFR, PDGFR, MET, CDK4, and PI3K/Akt pathway, in GBM. However, these small molecule inhibitors have been unsuccessful in improving patient outcome. Here, we investigate if crosstalk and redundancy in signaling pathways is responsible for single-agent resistance using patient-derived glioblastoma 2D stem cell cultures (pdGBM). Eight brain-penetrable and clinically approved small molecule inhibitors (SMI) were used to target key GBM driver genes. We measured cell viability in triplicate with a CellTiter-Glo assay. The half-maximal inhibitory concentration (IC50) for each inhibitor was defined for six molecularly distinct pdGBM 2D cell cultures. Although inhibition of downstream effector proteins reduced cell viability more effectively (IC50 70nM-1µM), compared to inhibiting upstream membrane-bound tyrosine kinase receptors (IC50 1-15µM), remaining cell proliferation was seen in all pdGBM using the different SMIs as single agent. To identify resistance mechanisms, we investigated changes in phosphokinase activity after SMI monotherapy in the different pdGBM 2D cell cultures. Based upon these results, we could identify combinations of SMIs targeting compensatory pathways that drive treatment resistance. In conclusion, this study presents a mechanistically driven selection of tumor tailored combination treatment to overcome resistance to SMI monotherapy in pdGBM. The efficacy of these novel SMI combinations will be challenged next, moving from pdGBM 2D stem cell cultures towards pdGBM organoids.
CNSC-32. SIMULTANEOUS INVESTIGATION OF TUMOR CELL BEHAVIOR AND CONNECTIVITY WITH CORRELATIVE IN VIVO TWO-PHOTON AND EX VIVO EXPANSION MICROSCOPY
Authors: Ekin Reyhan, Wolfgang Wick, Varun Venkataramani
Journal: Neuro-Oncology (2023)

Abstract Glioblastomas are the most aggressive primary brain tumors, characterized by whole-brain colonization, high therapeutic resistance, and inevitable recurrence. It has previously been shown that glioblastoma cells can form functionally gap-junction connected tumor cell networks with other tumor cells and/or astrocytes, which play a crucial role in tumor progression and treatment response. Furthermore, there is increasing evidence that synaptic neuron-glioma networks promote tumor growth. However, methodologies to investigate the direct link between synaptic, astrocytic and tumor cell connectivity together with tumor cell behavior including invasion, proliferation and therapeutic resistance are yet lacking. We aimed to characterize neuron-tumor and tumor-tumor/astrocyte cell interactions on a single cell level by using correlative in vivo two-photon and ex vivo expansion microscopy with near synaptic-resolution. We studied glioblastoma cells with intravital two-photon microscopy using patient-derived glioblastoma mouse models and the fluorescent functional imaging dye Sulforhodamine 101 allowing to investigate intratumoral and astrocytic connectivity over an extended period up to weeks. Subsequently, these functional tumor cell subpopulations could be directly correlated ex vivo to identify neuron-glioma synaptic connectivity. We utilized machine learning based segmentation and a semi-automated analysis pipeline to explore the connection of different glioblastoma morphological and behavioral subtypes to direct and indirect neuronal input in multiple xenograft models. With this new correlative method, we were able to simultaneously evaluate tumor cell behavior, synaptic and tumor-tumor/astrocyte connections on a single cell level. In addition, we demonstrated that this pipeline can be used for patient samples, revealing its clinical-translational potential for cancer neuroscience. In summary, we have established a new correlative technology that interlinks two key aspects of brain cancer neuroscience: cancer cell behavior and brain tumor network connectivity. This methodology promises a more thorough understanding of glioblastoma biology, facilitating the discovery of cancer biology, including the role of brain tumor networks in therapeutic resistance.
CTNI-36. SACITUZUMAB GOVITECAN FOR RECURRENT GLIOBLASTOMA
Authors: William Kelly, Henriette Balinda, Pegah Ghamasaee, Andrea Gilbert, Joel Michalek, Prathibha Surapaneni, John Floyd, Andrew Brenner
Journal: Neuro-Oncology (2023)

Abstract Glioblastoma (GBM) is an aggressive and highly malignant brain tumor characterized by its infiltrative growth, rapid progression, and poor prognosis. Sacituzumab govitecan (SG), an antibody-drug conjugate, has demonstrated antitumor activity and acceptable tolerability in patients with advanced epithelial cancers. It consists of a humanized anti-Trop-2 monoclonal antibody linked to a potent topoisomerase I inhibitor, SN-38. We conducted a prospective, single center, window of opportunity trial (NCT03995706) to examine the intra-tumoral concentrations of SN-38 in patients undergoing craniotomy for recurrent GBM (rGBM; n = 12). We enrolled patients aged ≥18 years diagnosed with rGBM to receive a single intravenous dose of SG at 10 mg/kg one day before surgical resection. Tumor and corresponding serum were collected during surgery to measure their levels of SN-38. Following recovery, patients resumed SG treatment at 10 mg/kg on days 1 and 8 of 21-day cycles and were accessed for responses by MRI every third cycle using response assessment in neuro-oncology (RANO) criteria. Trop-2 and carbonic anhydrase IX (CAIX) expression was investigated by IHC. An average of 2850.6 ng/ml in serum and 128.7 ng/g in tissue of SN-38 was quantified in our patient samples. Trop-2 expression was observed in 50% of patient tumors and 38% of the samples showed high expression of hypoxia marker CAIX. A strong positive correlation between the tissue/serum SN-38 and Trop-2 (r = 0.86, p = 0.01) was observed. Median overall survival of 17.5 months (0.9 - 28.5 months) and progression free survival of 2 months (0.5 - 12 months) were observed. A multicenter, phase II clinical trial has been initiated to further investigate the efficacy of SG in patients with breast brain metastasis. Updated data on response rates and accrual to the multicenter trial for rGBM will be presented
EPID-08. CLINICAL AND MOLECULAR DETERMINANTS OF BLEEDING-RELATED ADVERSE OUTCOMES IN HIGH-GRADE GLIOMA
Authors: Pushan Dasgupta, Justin Rousseau
Journal: Neuro-Oncology (2023)

Abstract Cancer is an independent risk factor for the development of venous thromboembolism (VTE) however patients with high-grade glioma (HGG) including glioblastoma (GBM) are at a particularly high risk of VTE with an incidence up to 20- 30% per year. Patients are often placed on anticoagulation to reduce the risk of VTE. However, patients with primary brain tumors such as HGG are at increased risk for intracerebral hemorrhage (ICH) even without the administration of anticoagulation. The combination of risk factors for ICH with anticoagulation and HGG complicates decision-making. Currently it is not known which of the direct oral anticoagulants (DOACs) are safest for patients with HGG in terms of adverse bleeding-related outcomes such as ICH. Furthermore, a deeper understanding of the clinical and molecular determinants of bleeding-related adverse outcomes in HGG is not fully characterized. In this study, we gathered data on patients with HGG from two Ascension Seton Hospitals in the Austin metro area from July 1, 2017 through June 30, 2022. We identified 76 pathology-confirmed patients with HGG. Patients who were on rivaroxaban (3/7 (43%), p=.022) had a statistically significant association with more bleeding-related adverse events compared to those on apixaban (0/12 (0%)) or enoxaparin (0/5 (0%)) even though the groups were similar in terms of their characteristics including total time on the respective anticoagulation. Patients on anticoagulation vs those never on anticoagulation did not differ in terms of their studied demographic and clinical characteristics. Intriguingly, logistic regression analysis revealed that patients harboring isocitrate dehydrogenase (IDH) mutations had a statistically significant association with more adverse bleeding-related events even when controlling for other relevant factors (Odds Ratio compared to reference GBM: 115.7; p=.014). This study offers insights into our understanding of relevant factors associated with worse bleeding-related adverse outcomes such as ICH in patients with HGG.
TMET-04. SENSITIZING DIPGS TO ANTIFOLATES: A PRECLINICAL STUDY ON PURINE BIOSYNTHESIS TARGETS
Authors: Ian Mersich, Sunny Congrove, Biplab Dasgupta
Journal: Neuro-Oncology (2023)

Abstract Diffuse Intrinsic Pontine Gliomas (DIPGs), among the most devastating pediatric brain tumors, present a desperate need for innovative treatment strategies, given the lack of effective therapies. Our study unveils a significant metabolic vulnerability in DIPGs, rooted in purine biosynthesis, a key facilitator of tumor progression. Contrary to prior reports, we demonstrate DIPG cell lines' sensitivity to methotrexate, an antifolate that targets purine metabolism, underscoring a potential reappraisal of its therapeutic role. Further, our research reveals a promising therapeutic synergy between antifolates, namely methotrexate and LSN-3213128, and SHMT inhibition, offering a potential novel treatment combination. This synergy, demonstrated in a proof-of-concept study, curtailed tumor progression in our DIPG mouse model, underscoring a promising new treatment strategy. Importantly, we identify a paradoxical antifolate resistance mechanism: while typical resistance is linked to dysfunctional folate transport, our findings intriguingly show an upregulation of folate transporters and intracellular folate in DIPGs. This paradox suggests that elevated intracellular folate levels may be effectively outcompeting antifolate metabolites for their targets. Significantly, the failure of physiological concentrations of purines in the cerebrospinal fluid (CSF) to restore DIPG cell viability under antifolate treatment further reinforces our rationale for targeting purine metabolism. The resistance mechanism is further validated by the observed synergy with SHMT inhibition, which disrupts the folate cycle allowing for the antifolates to out-compete the intracellular folates for their intended target. Our findings challenge conventional wisdom, open new avenues in DIPG therapeutic strategy, and highlight a paradoxical antifolate resistance mechanism that necessitates further exploration in the field.
NCOG-33. GLIOBLASTOMA AND PARKINSONISM, IS DEPLETED DOPAMINE A PROTECTIVE SURVIVAL FACTOR? A CASE SERIES OF 3 GBM PATIENTS
Authors: Jose Carrillo, Naveed Wagle, Akanksha Sharma, Minhdan Nguyen, Judy Truong, Emmaline Mauritson, Iryna Singh, Tiffany Juarez, Santosh Kesari
Journal: Neuro-Oncology (2023)

Abstract Glioblastoma multiforme (GBM) is the most common malignant brain tumor, and carries a grave prognosis with a median survival of 15 months. The pathophysiologic hallmark of Parkinson’s disease is neuronal loss of dopamine producing cells in the substantia nigra. Dopamine has been shown to modify cell-cycle status in neural progenitor cells. Dopamine agonism is adequate to increase progenitor proliferation in the subventricular zone (SVZ). Dopamine receptor antagonists have antiproliferative effects. A few clinical trials use selective dopamine receptor D2 (DRD2) inhibitors. Parkinsonism can have organic etiologies like stroke or neoplasm, while idiopathic Parkinsonism is known as Parkinson’s disease. While uncommon to have dual diagnoses, we identified three patients with both GBM and Parkinsonism, all were IDH wildtype, 2 patients were MGMT methylated, mean age was 67 years. Our 3 patients have a combined median PFS of 23.4 months, mean PFS of 25.4 months, which compares favorably to historical control median PFS of 6.9 months. Our 3 patients with dual diagnosis have a median OS of 47.3 months, and mean OS of 43.7 months, which compares favorably to historical median OS of 14.6 months. One might expect a patient with a neurodegenerative disease like Parkinson’s disease and a highly malignant tumor like GBM to have an extremely poor prognosis, yet our patient cohort reveals the opposite. The improved overall survival in GBM patients with Parkinsonism supports further clinical research into selective dopamine receptor inhibitors.